[Endocardial endothelium modulates lysophosphatidylcholine induced positive inotropism]

In isolated guinea pig papillary muscles, the endocardial endothelium (EE) was selectively damaged by exposing the muscles to a flow of dry air for 30s for removal of function EE. The results showed that LPC induced positive inotropic effect on papillary muscles was observed in a concentration-and time-dependent manner [PT after 15 mins' exposure to 5, 10 and 20 mumol.L-1 lysophosphatidylcholine (LPC) was increased by 104 +/- 7%, 110 +/- 6% and 124 +/- 10%, respectively]. The positive inotropic effect of 10 mmol.L-1 LPC on papillary muscles denuded of EE was significantly enhanced (PT: 163 +/- 23% vs 130 +/- 17% after exposing to LPC for 30 min). Scanning and transmission electronic microscopic studies exhibited signs of EE damage of papillary muscles incubated with LPC 10 mumol.L-1 for 30 minutes, such as disruption of gap junction between overlapping EE cells, retraction of the cell borders, fenestration on the EE, and denudation of the subjacent basal lamina. The present study suggests that the EE may affect the LPC-induced contractibility of papillary muscle via its barrier function signs, in addition, the present data provides further evidence that LPC may be a trigger for some kind of biological active factor release form EE.